The long-term objective of this study is to offer to the field of early childhood education a systematic, data-driven, integrative intervention to improve school readiness among Spanish-speaking English Language Learners who are at risk of experiencing school difficulties. The specific aims of this study are to: (1) evaluate the efficacy of the Nuestros Ninos program on promoting language, literacy, math and socio-emotional outcomes of Spanish-speaking English language earners during the pre-kindergarten year; (2) examine the extent to which the effects of the prekindergarten intervention are maintained at entry into kindergarten and 1st grade for Spanish speaking English language learners; and (3) examine whether specific child, family, teacher, program and professional development factors moderate the effects of the intervention on the short-term (Pre-K) and longer-term (K and first grade) language, literacy, math and socio-emotional outcomes of Spanish speaking English language learners. The Nuestros Ninos Program consists of an array of intervention strategies designed to supplement core curriculum activities, and organized using a Response to Intervention approach, in two levels: classroom-wide and small groups. Teachers will participate in professional development that consists of: (1) acquisition of content knowledge on the propose intervention strategies, through a series of interactive training institutes, (2) ongoing support from a bilingual consultant to help teachers implement new intervention strategies in the classroom, and (3) opportunities for reflection and shared inquiry with other teachers through community of practice meetings. The project will evaluate the efficacy of the intervention and factors that mediate outcomes with a total of 520 Spanish-speaking preschoolers of Mexican and Central American descent and 65 teachers in North Carolina and California, over a period of five years. Eligible teachers and classrooms will be randomly selected to participate in either a treatment (n = 33) or control group (n = 32). All eligible ELL children enrolled in selected programs will be invited to participate, with the goal of recruiting at least eight children in each class. Eligible ELL children from treatment (n=264) and control classrooms (n=256) will participate in child assessments measuring the intervention effects on child outcomes. Children's outcome measures will assess gains in vocabulary, phonological awareness, letter and word recognition, math abilities, problem behavior, and social skills. Child assessments will be conducted using parallel instruments in Spanish and English.